The crewstation instrumentation panels for commercial and military aircraft, naval vessels and tracked and armored vehicles, like many other display systems, frequently employ illuminated indicators and controls. The illumination may be optically filtered to produce a wide range of human visible or night vision imaging system (NVIS) colors, including blue, green, yellow, red and white or the NVIS colors of NVIS blue, NVIS white, NVIS green A (blue-green), NVIS green B (green), NVIS yellow (yellow) and NVIS red (orange-red). In addition, multiple lamps are used within the same display to illuminate different regions of the display separately, providing, for example, four separate legends, each individually illuminated, on the same display for a single illuminated pushbutton switch, indicator or annunciator.
Within dedicated legend illuminated pushbutton switches, for example, the legend is typically illuminated to indicate a first condition or state, and non-illuminated to indicate a second condition or state. For instance, illumination of the legend indicates actuation of the switch to a “closed” state, while the hidden or non-illuminated legend indicates that the switch is in an “open” state.
Color filters are often employed to adjust the spectral radiance of the illumination source(s) to meet the desired chromaticity coordinates and luminance levels at maximum rated voltage(s). By combining multiple illumination sources and different color filters, displays can have multiple legends that each light in a different color.
In many situations, it is desirable to have the legend for a pushbutton switch remain illuminated but use different indicia to indicate the state of the switch or the corresponding element controlled by the switch, such as by changing the color of the illumination.
There is, therefore, a need in the art for programmable illumination of dedicated legend pushbutton switches in which a single legend may be selectively illuminated in any of at least two different colors.